The objective of this project is to investigate the role of acetylcholine and amino acids as synaptic transmitters in the outer plexiform layer of the goldfish and turtle retina. The approach is multidisciplinary and will correlate results obtained from intracellular recording from horizontal and bipolar cells in response to pharmacological manipulations, assays for receptor binding to radiolabeled ligands for acetylcholine and the amino acid transmitter candidates: L-glutamate, glycine and GABA, and the localization of the receptors for these compounds by autoradiography. It is expected that this research will answer the question as to how lateral and centripetal information is encoded in the distal retina of these vertebrates.